1. Technical Field of the Invention
This invention relates to an apparatus and method of anchoring uprights in the ground and, more particularly, to a removable screw-type, in-ground anchor device that provides a secure foundation for uprights in any type of soil without using concrete.
2. Description of Related Art
At present, most uprights such as fence posts and sign posts are anchored in the earth by digging or drilling a hole in the ground, pouring concrete in the hole, and securing the base of the upright in the concrete until it dries. The process is tedious, labor intensive, and causes additional delays due to the drying and curing time of the concrete. Additionally, the uprights are extremely difficult or impossible to remove if the fence or sign post needs to be taken down or repositioned at a future date.
Past attempts to improve the foundation and anchoring of uprights have met with only limited success. A typical attempt is described in U.S. Pat. No. 5,295,766 to Tiikkainen. Tiikkainen discloses a foundation for uprights that includes a tubular drive-shaft that is equipped with a large helical auger at the base. In operation, a conical section above the auger serves to compact a soil layer softened by the rotation of the helical auger. However, the diameter of the auger is much greater than the widest diameter of the conical section and the outside diameter of the tubular drive-shaft. Therefore, the auger softens the soil surrounding the drive-shaft for a considerable distance beyond the outside diameter of the shaft. The conical section is then unable to compact the soil sufficiently to provide a secure foundation for the upright. Additional steps such as pouring concrete must be taken to reinforce the foundation. Thus, the soil conditions in which Tiikkainen can operate are limited, and Tiikkainen does not teach or suggest a screw-type, in-ground anchor device that provides a secure foundation for uprights without the use of reinforcing concrete.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a removable screw-type, in-ground anchor device that provides a secure foundation for uprights such as fence posts, sign posts, and street lights in any type of soil without using concrete. The present invention provides such a device.
In one aspect, the present invention is a removable screw-type, in-ground anchor device that provides a secure foundation for uprights such as fence posts, sign posts, and street lights in any type of soil without the necessity of using concrete. The anchor device includes a generally cylindrical drive shaft with a set of screw threads (flightings) mounted near the lower end. The drive shaft includes a cylindrical housing portion of a first diameter at an upper end of the drive shaft for supporting the above-ground upright. A shallow-sloped conical portion connects the housing portion to a tip portion that has a second diameter substantially less than the first diameter. The conical portion has a surface with a diameter that decreases from the first diameter to the second diameter over a longitudinal distance that provides a slope to the surface of less than 20 degrees, and preferably in the range of 5-10 degrees. The flightings are attached to the tip portion and have a third diameter that is approximately equal to the first diameter. The flightings operate in soil to screw the anchor device into the ground when the device is rotated.
In another aspect, the present invention is a screw-type, in-ground anchor device for anchoring an above-ground upright in all types of soil. The anchor device includes a cylindrical upper housing portion with a diameter sized to accept the above-ground upright. A set of flightings are mounted near a bottom end of the anchor device, and impart downward force on the anchor device when the anchor device is rotated. The flightings having a diameter approximately equal to or less than the diameter of the housing portion. The flightings disrupt the soil in their wake, and a conical portion having a slope of less than 20 degrees, and preferably in the range of 5-10 degrees, outwardly compresses the soil in the wake of the flightings. The outward compression of the soil creates a tightly compressed soil shaft having the same diameter as the housing portion.